1. GOOD MORNING!!! (APES Review, 3/7/12, CAPT Week)
Our Plan for This Wednesday Morning…
1) EAT! EAT! EAT!
2) Lab Activity: Estimating Population Size
3) Lecture: Introduce Population Biology
4) Activity: Population Growth Activity
5) Calculation Practice – Growth Rate
6) Lecture: Human Population Dynamics
7) Activity (Computers): Age Structure Diagram
HW:
prb.org activity
Quiz/Test, TBD

2. POPULATION BIOLOGY Chapter 6
HUMAN POPULATION DYNAMICS
(Chapter 7 – See other PPOINT)

3. What Limits the Growth of Populations?
Intrinsic factors - Operate within or between individual organisms in the same species.
Extrinsic factors - Imposed from outside the population.
Biotic factors - Caused by living organisms.
Abiotic factors - Caused by non-living environmental components.
No population can continue to grow indefinitely because of limitations on resources and because of competition among species for those resources.

4. Populations Have Certain Characteristics (2)
Why Do Population Sizes Change?
Temperature
Presence of disease organisms or harmful chemicals
Resource availability
Arrival or disappearance of competing species

5. Populations Can Grow, Shrink, or Remain Stable (1)
Population size governed by
Births
Deaths
Immigration
Emigration
Population change =
(births + immigration) – (deaths + emigration)
Natality –
Production of new individuals .
Fecundity –
Physical ability to reproduce.
Fertility –
Measure of actual number of offspring produced.
Immigration –
Organisms introduced into new ecosystems.

6. Figure 5.B
Population size of southern sea otters off the coast of the U.S. state of California, 1983–2007. According to the U.S. Fish and Wildlife Service, the sea otter population would have to reach about 8,400 animals before it can be removed from the endangered species list. (Data from U.S. Geological Survey)
Fig. 5-B, p. 110

7. Environmental resistance
Carrying capacity (K)
Population stabilizes
Population size
Exponential
growth
Figure 5.11
No population can continue to increase in size indefinitely. Exponential growth (left half of the curve) occurs when resources are not limiting and a population can grow at its intrinsic rate of increase (r) or biotic potential. Such exponential growth is converted to logistic growth, in which the growth rate decreases as the population becomes larger and faces environmental resistance. Over time, the population size stabilizes at or near the carrying capacity (K) of its environment, which results in a sigmoid (S-shaped) population growth curve. Depending on resource availability, the size of a population often fluctuates around its carrying capacity, although a population may temporarily exceed its carrying capacity and then suffer a sharp decline or crash in its numbers. See an animation based on this figure at CengageNOW. Question: What is an example of environmental resistance that humans have not been able to overcome?
Carrying Capacity - Maximum number of individuals of any species that can be indefinitely supported in a given area.
Biotic Potential - Maximum reproductive rate of an organism.
Biotic
potential
Time (t)
Fig. 5-11, p. 111

8. No population can continue to increase in size indefinitely
No population can continue to increase in size indefinitely. Exponential growth (left half of the curve) occurs when resources are not limiting and a population can grow at its intrinsic rate of increase (r) or biotic potential. Such exponential growth is converted to logistic growth, in which the growth rate decreases as the population becomes larger and faces environmental resistance. Over time, the population size stabilizes at or near the carrying capacity (K) of its environment, which results in a sigmoid (S-shaped) population growth curve. Depending on resource availability, the size of a population often fluctuates around its carrying capacity, although a population may temporarily exceed its carrying capacity and then suffer a sharp decline or crash in its numbers.. Question: What is an example of environmental resistance that humans have not been able to overcome?

9. Boom and Bust Cycles
Overshoot - Measure of extent to which population exceeds carrying capacity of its environment.
Dieback - Negative growth curve.
Severity of dieback generally related to the extent of overshoot.

10. r-Adapted Species
Adapted to unstable environment.
Pioneers, colonizers
Niche generalists
Prey
Regulated mainly by extrinsic factors.
Low trophic level
Short life
Rapid growth
Early maturity
Many small offspring
Little parental care
Little investment in individual offspring.

11. K-Adapted Species
Long life
Slower growth
Late maturity
Fewer large offspring
High parental care and protection.
High investment in individual offspring.
Adapted to stable environment.
Later stages of succession.
Niche specialists
Predators
Regulated mainly by intrinsic factors.
High trophic level

12. Number of sheep (millions)
2.0
Population
overshoots
carrying
capacity
Carrying capacity
1.5
Population recovers
and stabilizes
Population
runs out of
resources
and crashes
Number of sheep (millions)
1.0
Exponential
growth .5
Figure 5.12
Logistic growth of a sheep population on the island of Tasmania between 1800 and After sheep were introduced in 1800, their population grew exponentially, thanks to an ample food supply. By 1855, they had overshot the land’s carrying capacity. Their numbers then stabilized and fluctuated around a carrying capacity of about 1.6 million sheep.
1800
1825
1850
1875
1900
1925
Year
Fig. 5-12, p. 111

13. 2,000 Population overshoots carrying capacity 1,500 Population crashes
Number of reindeer
1,000
500
Carrying
capacity
Figure 5.13
Exponential growth, overshoot, and population crash of reindeer introduced to the small Bering Sea island of St. Paul. When 26 reindeer (24 of them female) were introduced in 1910, lichens, mosses, and other food sources were plentiful. By 1935, the herd size had soared to 2,000, overshooting the island’s carrying capacity. This led to a population crash, when the herd size plummeted to only 8 reindeer by Question: Why do you think this population grew fast and crashed, unlike the sheep in Figure 5-12?
1910
1920
1930
1940
1950
Year
Fig. 5-13, p. 112

14. Carrying capacity K K species; experience K selection
Number of individuals
r species;
experience
r selection
Figure 5.14
Positions of r-selected and K-selected species on the sigmoid (S-shaped) population growth curve.
Time
Fig. 5-14, p. 112

15. Figure 5.15
Population cycles for the snowshoe hare and Canada lynx. At one time, scientists believed these curves provided circumstantial evidence that these predator and prey populations regulated one another. More recent research suggests that the periodic swings in the hare population are caused by a combination of top-down population control—through predation by lynx and other predators—and bottom-up population control, in which changes in the availability of the food supply for hares help determine hare population size, which in turn helps determine the lynx population size. (Data from D. A. MacLulich)
Fig. 5-15, p. 114

16. No Population Can Grow Indefinitely: J-Curves and S-Curves (1)
Biotic potential
Low
High
Intrinsic rate of increase (r)
Individuals in populations with high r
Reproduce early in life
Have short generation times
Can reproduce many times
Have many offspring each time they reproduce

17. No Population Can Grow Indefinitely: J-Curves and S-Curves (2)
Size of populations limited by
Light
Water
Space
Nutrients
Exposure to too many competitors, predators or infectious diseases

18. Density Dependent Factors
Higher proportion of population is affected as population density increases.
Predation
Parasitism
Infectious disease
Competition for resources
Tend to reduce population size by decreasing natality or increasing mortality.
Interspecific Interactions
Predator-Prey oscillations
Intraspecific Interactions
Territoriality
Stress and Crowding
Stress-related diseases

19. Density Independent Factors
Constant proportion of the population is affected regardless of population density.
Tend to be abiotic components.
Do not directly regulate population size.
EXAMPLES:

20. Sample Problem: A population of birds was measured to be 1500 birds
Sample Problem: A population of birds was measured to be 1500 birds. Over the course of a year, there were 300 births and 200 deaths birds entered the population by migration, 50 birds left population by emigration.
How to Calculate Change in Population Size
How to Calculate Growth Rate of a Population:
Calculating R from CBR and CDR
How to Calculate Doubling Time of a Population:

21. No Population Can Grow Indefinitely: J-Curves and S-Curves (3)
Environmental resistance
Carrying capacity (K)
Exponential growth
Logistic growth

22. Genetic Diversity Can Affect the Size of Small Populations
Founder effect
Demographic bottleneck
Genetic drift
Inbreeding
Minimum viable population size

23. Under Some Circumstances Population Density Affects Population Size
Density-dependent population controls
Predation
Parasitism
Infectious disease
Competition for resources

24. Several Different Types of Population Change Occur in Nature
Stable
Irruptive
Cyclic fluctuations, boom-and-bust cycles
Top-down population regulation
Bottom-up population regulation
Irregular

25. Survivorship Curves

26. Humans Are Not Exempt from Nature’s Population Controls
Ireland
Potato crop in 1845
Bubonic plague
Fourteenth century
AIDS
Global epidemic

27. Case Study: Exploding White-Tailed Deer Population in the U.S.
1900: deer habitat destruction and uncontrolled hunting
1920s–1930s: laws to protect the deer
Current population explosion for deer
Lyme disease
Deer-vehicle accidents
Eating garden plants and shrubs
Ways to control the deer population

28. Core Case Study: Southern Sea Otters: Are They Back from the Brink of Extinction?
Habitat
Hunted: early 1900s
Partial recovery
Why care about sea otters?
Ethics
Keystone species
Tourism dollars

29. LOOK NO FURTHER…
ALL OF THE INFORMATION ON the SLIDES FOLLOWING THIS ONE WILL NOT BE ON THE POPULATION TEST!

30. 5-1 How Do Species Interact?
Concept 5-1 Five types of species interactions—competition, predation, parasitism, mutualism, and commensalism—affect the resource use and population sizes of the species in an ecosystem.

31. Species Interact in Five Major Ways
Interspecific Competition
Predation
Parasitism
Mutualism
Commensalism

32. Most Species Compete with One Another for Certain Resources
Competition
Competitive exclusion principle

33. Most Consumer Species Feed on Live Organisms of Other Species (1)
Predators may capture prey by
Walking
Swimming
Flying
Pursuit and ambush
Camouflage
Chemical warfare

34. Most Consumer Species Feed on Live Organisms of Other Species (2)
Prey may avoid capture by
Camouflage
Chemical warfare
Warning coloration
Mimicry
Deceptive looks
Deceptive behavior

35. Science Focus: Why Should We Care about Kelp Forests?
Kelp forests: biologically diverse marine habitat
Major threats to kelp forests
Sea urchins
Pollution from water run-off
Global warming

36. Predator and Prey Species Can Drive Each Other’s Evolution
Intense natural selection pressures between predator and prey populations
Coevolution

37. Some Species Feed off Other Species by Living on or in Them
Parasitism
Parasite-host interaction may lead to coevolution

38. In Some Interactions, Both Species Benefit
Mutualism
Nutrition and protection relationship
Gut inhabitant mutualism

39. In Some Interactions, One Species Benefits and the Other Is Not Harmed
Commensalism
Epiphytes
Birds nesting in trees

40. 5-2 How Can Natural Selection Reduce Competition between Species?
Concept 5-2 Some species develop adaptations that allow them to reduce or avoid competition with other species for resources.

41. Some Species Evolve Ways to Share Resources
Resource partitioning
Reduce niche overlap
Use shared resources at different
Times
Places
Ways